This month’s shooting at YouTube’s headquarters, which left four people injured and one person dead, rattled Silicon Valley. But for Dr. Andre Campbell, a trauma surgeon at Zuckerberg San Francisco General Hospital and Trauma Center where three of the victims were taken following the shooting, gun violence is a daily reality.

“Gun violence happens every day throughout the United States,” Campbell told reporters at a press briefing organized shortly after the shooting. “But I don’t see you guys out here — because I’d like to make sure that people know that we got a serious problem that we need to address.”

Campbell, who has worked at Zuckerberg San Francisco General Hospital for over 20 years and is also a professor of surgery at the University of California San Francisco, calls gun violence a public health problem. “We have to figure out a way for the weapons to not cause the damage that they do right now,” he tells The Verge in an interview. “I’m pretty expert at dealing with gunshot wounds, which is not something you want to become expert at.”

The Verge spoke with Campbell about his job caring for the victims of gun violence, the dangers of unchecked bleeding, and what injuries from high-velocity bullets look like.

The following interview has been edited and condensed for clarity and brevity.

You seemed surprised to see so many journalists at the press briefing after the shooting at YouTube. Why was that?

The reason why I was surprised is that every day, trauma providers around the country are confronted by people who are gunshot wound victims. A couple weeks before, we had a fairly large shooting where six people were injured and brought to the hospital. But there wasn’t as much attention at the hospital about what happened.

And when I was walking down the driveway to meet the press with our media folks, it just kind of occurred to me that it seemed like an awful lot of cameras, and video equipment for this, and I just wondered out loud about, ‘Wow this is a lot of media attention.’ But the reality is that this happens all the time, and you don’t show up for all that. You showed up for this, which is fine, it was terrible what happened to these poor folks who got injured, but the reality is that you don’t show up for that all the time.

So I was wondering about that out loud, when all of a sudden people were a little surprised that I even have an opinion about that. And they weren’t expecting someone to basically say what trauma providers around the country and around the world feel: that this is a common problem, and it is something we need to have solutions for.

Has it gotten to the point where you can recognize different guns by the injuries that you see?

The reality is if someone is shot by a high-velocity, high-caliber weapon, it creates massive destruction. I’ve seen some of those, but it’s hard to really tell. The holes are small going in, and they’re very large coming out.  So those are real, severe injuries that folks have, right? But I can’t really tell from looking at the wounds unless it’s something that’s really, really big. I can tell that most of the people we have who are injured are shot by handguns, and the handguns, they cause a fair amount of injury when you’re shot.

How do the injuries differ for the handguns versus the high-velocity weapons?

One of the ways that it’s described is if a high-velocity [bullet] hits your liver, it basically looks like you have dropped a watermelon from standing position to the ground, and it just basically explodes — it kind of blows up. And that’s what your liver looks like if it hits it. Whereas if you’re shot with a handgun in your liver, there’s a cone of destruction that’s about a centimeter around and it goes through the liver in that fashion.

What’s harder to treat?

When somebody has a high-velocity weapon, it’s much harder. But everything really depends on where the patient is shot or injured. If they’re shot in a vital organ, it only takes a bullet in a bad position for someone to die. So if you’re shot in a major vessel, like the aorta, or the vena cava, or the carotid artery, or the femoral artery, you can just bleed to death from that.

As a trauma surgeon, what do you wish that people knew about the kind of destruction that bullets can do to the body?

We all go into trauma surgery because we’re trying to save people’s lives and get them back to their family. And what happens is unfortunately when you are shot with a weapon, this can cause irreparable damage. You can have a head injury, you can have major destruction, you can have loss of function in your arms or legs, depending on if your spinal cord is injured and what [the] location is; you can obviously die if you have a massive hemorrhage, and you have catastrophic injuries to vital organs. Things can happen that can change a life in a second.

We’re pretty good at doing what we do. But it’s better not getting shot than getting shot and having us fix you. We’re pretty good at taking care of folks when they’re injured, but we’re not perfect.

Say someone comes in with a bullet wound, what is the most important thing to do first?

We evaluate their airway, we look at their breathing, we look at their circulation and we look [at] whether they’re disabled or not. And then we basically expose them, and we look everywhere to make sure that we don’t miss any holes anywhere. Then we do an assessment from head to toe. Look at their head, look at their neck, look at their chest, look at their abdomen, look at their pelvis and their legs, and we flip them over to see whether or not we have gotten every single area of their body examined.

And then, at that point, then we begin to decide what needs to be done. Does the patient need to go to the operating room? Do do they go to the CT scanner? If the wound is tangential and they’re stable, do they need to go to radiology or do they need to go to the operating room? So that’s what we are doing, as we’re trying to sort out what happened to the patient.

Before the patient gets to the hospital, is there anything that bystanders can do if someone’s been shot near them?

There are a series of things that happen when there’s a gunshot wound in the vicinity. The first is thing is that the police have to secure the area, number one. Then the paramedics will come in. The main thing is that people cannot become additional victims after a shooting happens. You have to basically stay out of the way and make sure you’re not another victim.

Once things are safe, then there are things you can do [with training from a program called Stop the Bleed]. You can compress with a t-shirt, preferably a clean one. You can pack the wound if you can, and then you can apply a well-placed, professional tourniquet if they have extremity — or arm and leg — wounds. That’s something a bystander can do to help. But you have to have some training, you can’t just do it out of your love for trying to help mankind. You need training, like anything. You want to do the right thing to try and save people, you don’t want to make anything worse.

Is there anything else that you wish people knew about your job, especially having to do with gunshot victims?

I’m a trauma surgeon, but I don’t work in isolation. We have a very sophisticated trauma system that’s been developed over the last 30 to 40 years. The system consists of paramedics around the field, it consists of firefighters who help the paramedics. It consists of the emergency department, the operating room, the ICU, and the rest of the hospital. And then after we’ve done everything, the patients then go to rehabilitation where they basically learn how to do the things that maybe were compromised after they got shot — they may have to learn how to walk, they may have to learn to get their strength together. There are all sorts of things that happen after they’re injured. There are literally hundreds of people involved in the care of the patient when something like this happens. You’re talking to me now, but I am just one of many people who’s involved in caring for these folks after they’ve been injured.

If you had one message about the toll of gun violence, what would you say?

The main thing is that too many people are shot, it’s a public health problem, and this current situation is bad for our patients. That’s the message that I want to say. Being shot is a terrible thing. We’ve gotten pretty good at fixing people. But we can’t save everybody, and that’s the hardest part about doing what I do is that, sometimes I look at somebody and I know I can’t save them, and that’s really hard.